ZCZC AP30
QST de W1AW
Propagation Forecast Bulletin 30 ARLP030
From Tad Cook, K7VVV
Seattle, WA July 28, 2000
To all radio amateurs
SB PROP ARL ARLP030
ARLP030 Propagation de K7VVV
Solar flux and sunspot numbers were down only slightly this week from last. Last week's average sunspot numbers were up over 40 points from the previous week, and this week's are down less than 7. But the big news this week should be the big peak in sunspot numbers on Thursday, July 20, when it reached 401. This is a rare, high number in any solar cycle, and the biggest so far in cycle 23.
A cursory examination of the data shows that the sunspot number has not been this high since August 23, 1991, when it was 478. Sunspot numbers over 400 suggest that we may be nearing the cycle peak.
The latest projection the author has seen for cycle peak is from the July 4 Preliminary Report and Forecast of Solar Geophysical Data from the NOAA Space Environment Center (on the web at http://www.sec.noaa.gov/weekly/index.html ). It shows smoothed monthly solar flux peaking in August or September, but smoothed sunspot numbers peaking around next January or February.
The latest short term projections show some rough weather ahead for the weekend, with the planetary A index for Friday through Tuesday at 30, 25, 12, 12 and 10. Projected solar flux for those same five days is 160, 155, 155, 150 and 145. Solar flux should rise above 200 by August 4, then reach 230 on August 8-14, and peak around 235 on August 15-16.
WF7M wrote to ask about geomagnetic indices for Alaska. This is identified as the College index at gopher://solar.sec.noaa.gov/00/latest/DGD . These values are generally higher than the mid-latitude or planetary indices.
The author of this bulletin is off on a short vacation via train, and next week K9LA has graciously agreed to write the bulletin.
Sunspot numbers for July 20 through 26 were 401, 325, 290, 276, 215, 232 and 214 with a mean of 279. 10.7 cm flux was 252.9, 250.9, 251, 217.3, 224.8, 201.8 and 174.6, with a mean of 224.8, and estimated planetary A indices were 43, 9, 18, 20, 8, 7 and 20, with a mean of 17.9.